Method of removing manganese oxide deposits

ABSTRACT

A METHOD OF REMOVING MANAGNESE CONTAINING DEPOSITS FORMED ON THE SURFACES OF JET ENGINES FROM BURNING FUEL CONTAINING A CYCLOPENTADIENYL MANGANESE TRICARBONYL AS A SMOKE REDUCER; BY TREATING THE DEPOSIT COATED SURFACES WITH AN AQUEOUS SOLUTION OF A MINERAL ACID AN ORGANIC ACID HAVING AN IONIZATION CONSTANT AT 25*C. GREATER THAN 10**-3, EITHER IN THE PRESENCE OR ABSENCE OF H2O2 OR AN H2O2 SOURCE AS A PROMOTER.

l i l 1 1 United States Patent US. Cln 134-41 9 Claims ABSTRACT OF THE DISCLOSURE A method of removing manganese containing deposits formed on the surfaces of jet engines from burning fuel containing a cyclopentadienyl manganese tricarbonyl as a smoke reducer, by treating the deposit coated surfaces with an aqueous solutionof a mineral acid, an organic acid having an ionization constant at 25 C. greater than 10- either in the presence or absence of H 0 or an H 0 source as a promoter.

CROSS REFERENCE TO RELATED APPLICATION This application is' a continuation-in-part of SN. 692,- 270, filed Dec. 21, 1967, now US. 3,556,846.

BACKGROUND OF THE INVENTION Smoke produced during the operation of a distillate fuel burning engine, such as a jet engine, is undesirable. It contributes to air pollution. It indicates reduced engine efficiency.

This exhaust smoke may be reduced by adding suitable additives to the fuel. Especially effective additives are certain cyclopentadienyl manganese tricarbonyls, such as (methylcyclopentadienyl)manganese tricarbonyl. US. 2,818,417 provides a thorough list of useful compounds of this type, and includes methods of preparing them. Although use of these manganese additives substantially reduces the exhaust smoke, a secondary problem may arise in some instances. On combustion of the fuel containing the manganese compound, manganese containing deposits are formed on the engine surface which are contacted by the exhaust products. As with many engine deposits, an effective method of removing these manganese containing deposits is desirable.

SUMMARY OF THE INVENTION A method of removing manganese containing deposits formed on the surfaces of jet engines which burn fuels containing organo manganese compounds, which comprises treating the deposit coated surfaces with an aqueous solution of a mineral acid,'a halogenated monocarboxylic acid, or an alkyl or aryl sulfonic acid, either with or without hydrogen peroxide as a promoter.

Thus, manganese containing deposits formed in jet engines can be removed for example, by treating the deposit coated surfaces with an aqueous solution of trichloroacetic acid or trichloroacetic acid and hydrogen peroxide. This provides a simple and effective method for cleaning the engine; it is especially advantageous because the engine can be cleaned without disassembling it.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this invention is a method of removing manganese containing deposits formed on the surfaces of a jet engine from burning a fuel containing a smoke reducing quantity of a cyclopentadienyl manganese tricarbonyl having up to 17 carbon atoms, which comprises treating said surface with an aqueous solution of an 3,682,702 Patented Aug. 8, 1972 acid selected from simple inorganic mineral acids and organic acids (a) having an ionization constant, at 25 C., greater than 10- and (b) having a formula selected from R-COOH wherein R is a group selected from halogen-substituted C -C alkyl and halogen-substituted phenyl, and

wherein R is a group selected from C -C hydrocarbon alkyl, phenyl, and C C hydrocarbon alkyl-substituted phenyl.

Another embodiment of said method comprises treating the manganese containing deposit coated surface with an aqueous solution containing up to about 30 percent by weight of the acids described above.

In another embodiment, the method described above is carried out using the aqueous acid solution containing a promoter quantity of hydrogen peroxide. The promoter is present in a quantity by weight from 0.1 to 1 times the weight of the acid.

In a preferred embodiment using either the promoted or unpromoted aqueous solution, the acid is a mineral acid selected from sulfuric acid and phosphoric acid. In another preferred embodiment the acid is a halogenated acetic acid.

Manganese compounds which are useful as smoke reducers in jet fuels are cyclopentadienyl manganese tricarbonyls having the formula RM (CO) 3 wherein R is a cyclopentadienyl hydrocarbon radical having from 5 to 17 carbon atoms. US. 2,818,417, issued Dec. 31, 1957, contains an extensive disclosure of the.

' fuels having a higher end point than gasoline. They are generally composed of distillate fuels and naphthas and blends of the above, including blends with lighter hydrocarbon fractions. The end point of preferable jet fuels is at least 435 F. and more preferably greater than 470 F.

Typical jet fuels include JP-3, a mixture of about 70 percent gasoline and 30 percent light distillate having a percent evaporation point of 470 F.; JP-4, a mixture of about 65 percent gasoline and 35 percent light distillate especially designed for high altitude performance; JP5, an especially fractionated kerosene and the like.

The manganese containing deposit which is formed on the jet engine surfaces can comprise a mixture of compounds. Principal components of this mixture are the oxides such as M11 0 and Mn O Acids which are used in this invention include inorganic mineral acids as well as organic acids. Useful inorganic mineral acids are exemplified by sulfuric acid, sulfurous acid, the hydrohalide acids such as HCl, HBr, and the like, orthophosphoric acid, pyrophosphoric acid, phosphorous acid and the like, nitric acid, orthoboric acid,

rnctaboric acid and the like. Sulfuric acid and orthophosphoric acid are preferred acids. OTgafiic acids which are useful (1) have an ionization constant (K) at 25 C. greater than 10" and (2) contain the elements C, H, O and X, where X is a halogen. This invention can also be extended to acids such as 2-methyl-6-nitrobenzoic acid, picric acid glycerophosphoric acid, o-nitrobenzoic acid, ethyl dihydrogen phosphate, dibutyl hydrogen phosphate, propyl phosphonic acid and the like.

Preferred organic acids are the halogen-substituted monocarboxylic acids having Formula I. The halogen substituent can be iodine, fluorine, chlorine or bromine. The acid may contain one or more halogen atoms. Examples of useful acids are o-iodobenzoic acid, a-bromopropionic acid, a,a-difluorohexanoic acid, p-iodobutyric acid, a-fiuoropentanoic acid, fl,fi-dichlorohexanoic acid, 3,5-diodobenzoic acid and the like. More preferred organic acids are the halogenated acetic acids. These in clude chloroacetic acid, dichloroacetic acid, bromoacetic acid, iodoacetic acid, fiuoroacetic acid, difiuoroacetic acid, dibromoacetic acid, trifiuoroacetic acid, tribromo acetic acid, triodoacetic acid and the like. A most preferred halogenated acetic acid is trichloroacetic acid.

Another group of preferred organic acids are the sulfonic acids having Formula II. These acids are aryl and alkyl 'substituted sulfuric acid, characterized generally by good water solubility. Both straight chain and branched chain hydrocarbon alkyl sulfonic acids are useful. Examples of useful alkyl sulfonic acids are ethane sulfonic acid, octadecane sulfonic acid, decane sulfonic acid, 1,l,3,3,5,5-hexamethylpentane sulfonic acid, octane sulfonic acid, tridecane sulfonic acid, l,1,3,3-tetramethylbutane sulfonic acid, l-methylundecane sulfonic acid, 2-methylpropane sulfonic acid and the like.

Useful aryl sulfonic acids are benzene and alkyl benzene sulfonic acids. Examples of useful acids are benzene sulfonic acid, p-toluene sulfonic acid, o-isobutylbenzene sulfonic acid, 2,4-diethylbenzene sulfonic acid, dodecylbenzene sulfonic acid, p-(1,l,3,3-tetramethylbutyl)benzene sulfonic acid, o-isopropylbenzene sulfonic acid, n-decylbenzene sulfonic acid, 2,6dimethylbenzene sulfonic acid and the like.

Phosphorous containing organic acids are also useful. These include the alkyl and aryl esters of orthophosphoric acid, phosphorous acid, phosphonic acid and the like. Examples of useful esters are methyl dihydrogen phosphate, methyl phosphonic acid, dimethyl phosphate, octadecyl phosphoric acid, phenyl dihydrogen phosphate, dibutyl hydrogen phosphate, dodecyl dihydrogen phosphate, octyl phosphonic acid, propyl dihydrogen phosphite, decyl phosphonic acid, phenyl phosphonic acid and the like.

In another embodiment of this invention, a promoter, hydrogen peroxide, is used in combination with either the inorganic or organic acid in aqueous solution. The hydrogen peroxide makes the aqueous acid solution more effective in removing the manganese containing deposit. The data presented below will illustrate this promoter effect.

Although hydrogen peroxide itself is most conveniently used, compounds which will produce hydrogen peroxide or the peroxide ion (OOH-) in an aqueous medium may also be used as promoters. Examples of such useful materials are inorganic compounds such as sodium peroxide, potassium peroxide, calcium peroxide, barium peroxide, copper peroxide, zinc peroxide, cadmium peroxide, mercury peroxide, super oxides of monoand divalent metals and the like; and organic peroxide compounds represented by the formula L-OOL and LO-H where L is a suitable alkyl or aryl radical, examples of which are dicumyl peroxide, cumyl hydroperoxide, perbenzoic acid, peracetic acid, performic acid, and the like.

The concentration of acid in aqueous solution is not critical. It can vary from about 0.001 percent to about percent by weight. Acid concentrations of from 5-10 percent by weight are conveniently used.

The concentration of hydrogen peroxide used as a promoter in this invention is based on the weight of acid used. Generally, the weight of hydrogen peroxide can range from about 0.1 to about one times the weight of acid present. For example, a 10 weight percent aqueous solution of dichloroacetic acid containing from about one percent to about 10 percent hydrogen peroxide is useful. Solutions containing equal amounts by weight of acid and hydrogen peroxide are especially useful. Where a compound which will produce the hydrogen peroxide in situ is used instead of the hydrogen peroxide itself, a. sufiicient amount of this hydrogen peroxide source is used to provide hydrogen peroxide in the above described concentration range.

An outstanding feature of the present invention is that it offers a method of removing manganese containing deposits in a jet engine without requiring its disassembly or its removal from its mounting. Thus, the engine can be cleaned while it is still in place in an airplane fuselage for example, by simply spraying a solution of acid or acid and hydrogen peroxide described above, through the en gine, while the engine is being cranked. cranking a jet engine means that the engine is turning but the fuel is not ignited. By cranking the engine, all the engine surfaces which may have a manganese containing deposit become exposed to the spray.

Another method of spraying the solution into the jet engine is to feed it through the fuel feed system between the fuel tank and the combustion area. Using this procedure, the solution will contact only those engine surfaces on which the fuel and exhaust products would impinge. The engine is cranked to insure better contact. In either case, the spray may be continuously recycled if desired, to reduce the volume of solution required. Besides the spraying technique, the engine can be cleaned by immersing it in a suitably designed vessel containing the acid or acid/hydrogen peroxide solution for a period of time sufficient to dissolve the manganese containing deposits. After such an immersion or after a spray treat ment, the engine is generally rinsed with pure water. A combination of the spray-soak procedure can also be used.

The engine treatment can be carried out either before or after the engine has cooled after being in operation. The solution with which the treatment is carried out may also be warmed, if desired. By treating the engine whilehot or by using a hot solution, treatment time to clean the engine can be reduced. Heating either the engine surfaces or the solution, however, is not required. Whatever means is used to carry out the engine treatment, the only requirement is that a solution, as herein described, contact the manganese containing deposits on the engine surfaces.

The effectiveness of the acid or acid/hydrogen peroxide aqueous solution treatment was determined in a laboratory procedure using a metal test specimen on which was deposited a manganese-containing deposit. The test specimen was prepared by allowing the exhaust stream from buring a jet fuel containing about 0.1 volume percent (1.29 g./ga1. of manganese) of (methylcyclopentadienyl) manganese tricarbonyl, to impinge on the metal piece. The manganese containing deposit appeared as a brownish deposit on the metal surface. This test specimen was then placed in a chamber where it was subjected to an alternate spray/soak treatment. This treatment consists of (a) spraying (1.48 gal. per hour at 10 p.s.i.g.) the test piece with the test solution for five minutes while the test piece is spinning and (b) then allowing the wet specimen to set for an additional five minutes; this spray/soak cycle is repeated three times. At the end of the treatment cycle, the test piece is rinsed with clear water and is then allowed to dry. The treated test piece is then weighed The loss in weight compared with the test piece before treatment represents the amount of deposit dissolved. This is recorded as percent deposit loss. Using this test procedure various acid and acid/hydrogen peroxide solutions were evaluated. The results are presented in the following table. -All percentages are by weight.

I All test solutions were at room temperature.

The data in Table 1 clearly illustrates the benefits of the present invention. Example 2 shows that a 10 percent aqueous solution of a mineral acid (H PO removed 36 percent of the manganese containing deposit. By adding 10 percent H to the 10 percent H PO the amount of deposit removed is almost doubled (64 percent). Examples 4 and illustrate the analogous effectiveness for an organic acid, trichloroacetic acid (K at 25 C.=l.3X-

andi trichloroaceticv acid promoted with hydrogen per- OXl e.

Deposit removal effectiveness similar to that illustrated by Examples 2 and 3 and 4 and 5 above is obtained when the following aqueous solutions are used for treating the manganese containing deposits. All percentages are by weight.

TABLE 2 Example Aqueous solution 6 0.001% HQBOJ. 7.. 0.001% H;BO; plus 0.001% H20: 8.. 0 0 H2504. :il)6 20g; H2504 D1113 10% H102.

my: mso. plus 1.5% 11.0.. 1% H4P201. 1 o 114F201 D1118 H201. 3% Hci plus 4% 11.0..

3% HNO3. HNO: P1113 H202. 1% HaPOg plus 0.25% H202.

19- 1% H51 0; plus 0.76% H201. 20. 0.5% HBr. 21, 0.5% HB: plus 0.5% H401. 22. 7% p-toluene sulfonic acid. 23. 7% p-toluene sulionic acid plus 2.5% H202. 24. 20% dichloro acetic acid. 25. 20% dichloro acetic acid plus NaZOz. 26 0.01% a-bromo propionic acid. 27 0.01% -bromo propionic acid plus 0.006% H202. 28- 30% trifluoro acetic acid. 29. 30% trifluoro acetic acid plus 30% H103. so 12% p-iodo butyric acid.

12% fl-iodo butyric acid plus 0.65% 11:02. 11% a,d-dichloro hexanoic acid 11% a d-dichloro hexanoic acid plus 2.8% B101. 6% mromo benzoic acid.

6% m-bromo benzoic acid plus 0.6% H101.

1% 2,4-dichloro benzoic acid.

1% 2,4-dich1oro benzoic acid plus 0.2% H10.

3s 1.5% p-iodo benzoic acid.

39 1.5% p-iodo benzoic acid plus 0.45% H10 40, 5% dimethyi hydrogen phosphate.

41 5% dimethyl hydrogen phosphate plus 2% 1120:.

42 0.07% butyl phosphonic acid.

43, 0.07% butyl phosphonic acid plus 0.06% B101.

44. 10% u-lDdO pentanoic acid.

45- 10% zrlOdO pentanoic acid plus 1.5% 1110:.

46, 0.02% octadecane sulionic acid.

47 0.02% octadecane sulionic acid plus 0.005% H10 48- 3% nonane sulfonic acid.

49 3% nonane sulfonic acid plus 1.8% Na o 50 10% butane sulfonic acid.

'5 10% butane sultonic acid plus 4% H102.

5 7% ethane sulfonic acid.

53 7% ethane sulfonic acid plus 7% H204.

54 4% (l,3-dimethyl)butaue sulfonic acid.

55 4% (l,3-dimethyl)butane sulfonic acid plus 4 0 H 0.

56 6% (2-methyl-4,4-dimethyl)pentane sulfonic acid.

57 6%H(%-methyl-4,4'dimethyl)pentane sulfonic acid plus 6% 53 2.5 (Z-methyl-4,4,6,6,8,8-hexamethyl)nonane sulfonic acid.

59 2.6 a (2-methyl-4,4,6,6,8,8-hexamethyl)nonane sulionic acid plus 1% H202.

m 12% benzene sull'onic acid.

TABLE 2-Contiuued llxuluplo Aqueous solution 61 12% benzene sulionic acid plus 7% NazOz.

62--- 25% 2,6dimethyl benzene sultonic acid.

63- 25% 2,6-dirnethyl benzene sulionic acid plus 23% H202. 64"-.. 3.5% p-dodecylbenzene suifonic acid.

66... 3.5% p-dodecylbenzene sulfonic acid plus 3% B202. 66. 4.5% o-ethyl benzene sulfonic acid.

67. 4.5% o-ethyl benzene sultonic acid plus 4.5% H202. 6S- 8% p-tert-butyl benzene sulionic acid.

69. 8% p-tert-butyl benzene sult'onic acid plus 5.2% H20 70. 13% decyl benzene sullonic acid.

71. 13% decyl benzene sultonic acid plus 7.8% H202.

72. 16% o-isobutyl benzene sulfonic acid.

73. 16% o-isobutyl benzene sulionic acid plus 16% H202. 74. 9% p-hexylbenzene sult'onic acid.

75 9% p-hexylbenzene sulionic aci plus 7.2% H102.

In each case, the acid solution containing the hydrogen peroxide removes significantly more manganese containing deposit than the acid solution without the promoter; the improvement in effectiveness (or the promoter effect) is of the same order as that illustrated by Examples 2 and 3 and 4 and 5.

The results presented above clearly demonstrate that the manganese containing deposits formed on jet engine parts can be effectively removed by treatment with an aqueous solution of acid as herein described. They further show the promoter effect of hydrogen peroxide in the acid solution. The manganese containing deposit has been described as that being formed from burning jet fuel containing a cyclopentadienyl manganese tricarbonyl. However, it is considered within the scope of the present invention that'the present method will be effective for removing manganese containing deposits obtained on burning jet fuel containing other manganese bearing additives.

The process of the present invention is described above. It is intended that the present invention be limited only within the lawful scope and extent of the following claims.

I claim:

1. A method of removing manganese containing deposits formed on surfaces of a jet engine from burning a fuel containing cyclopentadienyl manganese tricarbonyl compounds wherein said cyclopentadienyl radical has up to 17 carbon atoms, which comprises treating said surfaces with an aqueous solution which consists essentially of water and an inorganic mineral acid selected from the group consisting of sulfuric acid, sulfurous acid, the phosphor'ic acids, phosphorous acid, the boric acids, hydrochloric acid, hydrobromic acid, and nitric acid, wherein. said aqueous solution contains from about 0.001% to about 30% by weight of said acid.

2. The method of claim 1 wherein said acid is sulfuric acid. I

3. The method of claim 1 wherein said acid is 11 F 0 4. The method of claim 1 wherein said acid is orthophosphoric acid.

5. The method of claim 1 wherein said acid weight percent is about 5% to about 10%.

6. The method of claim 5 wherein said acid is sulfuric acid.

7. The method of claim 5 wherein said acid is H3 0 8. The method of claim 5 wherein said acid is ortho phosphoric acid.

9. The method of claim 8 wherein said acid weight percent is about 10%.

References Cited UNITED STATES PATENTS 3,556,846 1/ 1971 Hnizda 134----3 3,554,801 l/l97l Kleiman 134-3 3,526,545 9/.1970 Aboud, Jr. 134 -3 3,506,488 4/1970 Kleiman 134-3 MAYER WEINBLA'IT, Primary Examiner US. Cl. X.R.

l343. 22: 252-l00. 135, 136. I42.

0 mg UNITED STATES PATENT OFFICE 5 0 CERTIFICATE OF CORRECTION Patent No. 5, 2,702 Dated August 8, 1972 Inventofle) Vincent F.- Hnizda It is certified that error appears in the abcve-identified patent:

and that said Lefiters Patent are hereby corrected as shown below:

In Column 5, line 55 (Table 2, Example 32) ll/o on, d- 1 dichloro hexanoic acid" should be ll/o men-dichloro hexanoic acid In Column 5, line 56 (Table 2, Example 35) "ll/o d, ddichloro hexanoic acid plus 2.8 0 H 0 should be ll/o a,oL-dichloro hexanoic acid plus 2.8/o H 0 Signed and sealed this 19th day of December 1972.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M.FLETCHER,JR. Attesting Officer Po-ww UNITED sTATEs PATENT oEETcE CERTIFICATE OF coREEcTToN Patent No. 3, ,7 Q Dated August 8, l972 Inventqr(s) Vincent F. Hnizda It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

- F- In Column 5, line 55 (Table 2, Example 32) ll"/o 01,, d- 1 dichloro heXanoic acid should be ll/o OL,OL-diChlOI'O heXanoic acid In Column 5, line 56 (Table 2, Example 55) "ll/o OL, ddichloro hexanoic acid plus 2.8/o H 0 should be ll/o' d,ddichloro hexanoic acid plus 2.8/o H 0 Signed and sealed this 19th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

